The present invention relates to power supplies, and in particular, to multiphase converter power supplies, and even more particularly, to a multi-phase buck converter power supply for providing low voltage, high current power to such devices as portable computers such as notebook and laptop computers.
Multi-phase buck converter switching power supplies are now in use for providing low voltage, high current, high efficiency power supplies for such applications as portable computers, for example, laptops and notebook computers.
The present invention relates to a multi-phase converter power supply wherein current amongst two or more phases is automatically adjusted so that the multiple phases automatically adjust to share in the electrical current demanded by the load. Thus, the present invention provides a method and apparatus for allowing the multiple phases of a multi-phase buck converter power supply to share equally in providing power to the load. Thus, according to the present invention, if higher current is being demanded in one phase, the apparatus of the invention will automatically adjust the other phases so that the current supplied to the load is shared equally. Similarly, if a phase current demand is reduced, the other phases will be reduced accordingly.
In the prior art, IR's X-phase converter chips for buck converter power supplies are known. For example, the IR308X Series chip is known. In that chip series, a control chip controls a plurality of phase chips. Each phase chip drives a single phase of the multi-phase converter which are coupled to the DC output bus. For a two or three phase converter, two or three phase chips are used, respectively. However, for a two or three phase converter, there is more complexity than is necessary using these integrated circuits and multiple chips need to be used. Use of multiple chips provides flexibility for a converter having many phases, but is not necessary for a two or three phase converter. In particular, each integrated circuit in the X-phase series includes a current share adjust amplifier to ensure that the currents are shared equally by the phases. For a two or three phase converter, it is desirable to have a simpler system to ensure that the currents are shared by the multiple phases. In particular, it is desirable to reduce the number of error amplifiers used to achieve current sharing and to reduce the number of chips.